Docker Swarm程式碼分析筆記（13）——filter

這是一個建立於 的文章，其中的資訊可能已經有所發展或是發生改變。

Docker Swarm manage命令的filter選項用來指定scheduler選擇Docker Engine的過濾項，其變數定義如下（cli/flags.go）：

// hack for go vetflFilterValue = cli.StringSlice(filter.List())// DefaultFilterNumber is exportedDefaultFilterNumber = len(flFilterValue)flFilter = cli.StringSliceFlag{    Name:  "filter, f",    Usage: "filter to use [" + strings.Join(filter.List(), ", ") + "]",    Value: &flFilterValue,}

獲得filter值的代碼如下（cli/manage.go）：

// see https://github.com/codegangsta/cli/issues/160names := c.StringSlice("filter")if c.IsSet("filter") || c.IsSet("f") {    names = names[DefaultFilterNumber:]}fs, err := filter.New(names)if err != nil {    log.Fatal(err)}

預設情況下，獲得所有的filter（scheduler/filter/filter.go）：

func init() {    filters = []Filter{        &HealthFilter{},        &PortFilter{},        &SlotsFilter{},        &DependencyFilter{},        &AffinityFilter{},        &ConstraintFilter{},    }}

而Filter是一個interface（scheduler/filter/filter.go）：

// Filter is exportedtype Filter interface {    Name() string    // Return a subset of nodes that were accepted by the filtering policy.    Filter(*cluster.ContainerConfig, []*node.Node, bool) ([]*node.Node, error)    // Return a list of constraints/filters provided    GetFilters(*cluster.ContainerConfig) ([]string, error)}

其中Filter方法用來過濾合格Docker Engine，而GetFilters則返回一個描述過濾條件的字串。

在scheduler/filter/filter.go中，ApplyFilters用來過濾Docker Engine；listAllFilters返回所有的過濾條件：

// ApplyFilters applies a set of filters in batch.func ApplyFilters(filters []Filter, config *cluster.ContainerConfig, nodes []*node.Node, soft bool) ([]*node.Node, error) {    var (        err        error        candidates = nodes    )    for _, filter := range filters {        candidates, err = filter.Filter(config, candidates, soft)        if err != nil {            // special case for when no healthy nodes are found            if filter.Name() == "health" {                return nil, err            }            return nil, fmt.Errorf("Unable to find a node that satisfies the following conditions %s", listAllFilters(filters, config, filter.Name()))        }    }    return candidates, nil}// listAllFilters creates a string containing all applied filtersfunc listAllFilters(filters []Filter, config *cluster.ContainerConfig, lastFilter string) string {    allFilters := ""    for _, filter := range filters {        list, err := filter.GetFilters(config)        if err == nil && len(list) > 0 {            allFilters = fmt.Sprintf("%s\n%v", allFilters, list)        }        if filter.Name() == lastFilter {            return allFilters        }    }    return allFilters}